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Wall Cracks

AS2870 Residential Slabs and Footings Table C1 Classification of Damage with reference to Walls

(Damage Classification - Description & Remediation Recommendation - Approximate Crack Widths)

Negligible - hairline cracks - less than 0.1mm

Very Slight - fine cracks that do not need repair - 0.1 to 1mm

Slight - cracks noticeable but easily filled, doors and windows stick slightly - 1 to 5mm

Moderate - cracks can be repaired and possibly small amount of wall will need to be replaced, doors and windows stick, service pipes can fracture, weather tightness often impaired - 5 to 15mm (or multiple 3mm or more in a group)

Severe - extensive repair work involving breaking out and replacing sections of walls (especially over doors and windows), window frames and door frames distort, wall lean or bulge noticeably, some loss of bearing in beams, service pipes disrupted - 15 to 25mm

Common Potential Reasons:

- Ground surface movement; clay soils expand and shrink with change of moisture content, seasonal or from local sources

- Ground settlement; soil compresses with more loads, sand settles quickly, clay settles very slowly

- Additional long term movement of supporting structures; reinforced concrete and timber move more over the long term, unreinforced concrete and masonry move more over the long term and when cracked, metal have no additional long term movement

- Inadequate strength to resist applied loads; wall or supporting structures

- Thermal contraction and expansion

- Vibrations

When to Refer to a Structural Engineer:

- When crack widths of 10mm or multiple 6mm in a group are observed; to avoid potential unsafe conditions

- To improved serviceability or performance

- For formal reports; insurance, legal purposes, assurance or other reasons

Other Recommendations:

- For new construction notify your structural engineer your preferred wall cracking performance